1. Field of the Invention
The present invention pertains broadly to the field of direct current (DC) power supplies. In greater particularity, the invention relates to switching circuitry for controlling the application of backup DC power to a load.
1. Description of the Prior Art
Increasingly greater reliance upon electrical devices has made these items of greater and greater importance. For some applications, the effect of power interruption to a device can be tremendous. This is particularly true in military defense settings. As is well known, many electrical devices in defense applications are heavily relied upon to provide information at instantaneous rates. Lapses of power to these devices will result in not only terminating the receipt of this information but may also destroy ongoing calculations such as those that are stored in temporary electronic memory.
Once power shutdown occurs, restoration efforts must begin immediately or a substantial loss of information may occur and, in military scenarios, a loss of offensive or defensive capability.
As it is for many electrical devices, such as computers and the like, DC power is used as a source of energization energy. To prepare for the unexpected loss of power to these electrical components, it is typical that battery powered backup power supplies be utilized. In situations where backup power supplies are used, it is necessary that there be switching circuitry enabling a switch from system primary power to the auxiliary source of power.
In some military applications, as well as other non-military applications, it is desirable that switching circuitry permit an instantaneous diversion of system power. This, of course, is necessary so that no loss of circuit-supplied information or capabilities occurs.
Besides permitting such instantaneous transition, it is desirable that battery powered backup power supplies include disabling circuitry that cuts-off battery supplied power before excessive battery discharge is experienced.
Where such auxiliary battery power supplies may be in place for a substantial time it is also desirable that charger circuitry be provided to maintain the batteries at their optimum power levels. Additionally, in such circumstances, it is desirable that battery test circuitry be provided so that the battery power may be tested periodically to reveal battery charge status.